In foggy and hazy environment, birds are able to locate position of sun and their path by means of
In foggy and hazy environment, the visible spectrum of the sun is not able to penetrate and so, humans find it difficult to visualize. However, the UV-A can penetrate through the fog, which cannot be detected by human eyes as t falls behind the visible spectrum of VIBGYOR. Birds are capable of recognizing more colors than the humans, they can detect the UV rays as well that allows them to navigate in the foggy and hazy conditions as well. These also allow the birds to track their migratory routes.
Hence, the correct answer is 'Ultra-violet radiations'.